1. Field of the Invention
The present invention relates to an image readout lens used in an optical system of an image readout apparatus such as facsimile machine or image scanner, for example; and an image readout apparatus using the same. In particular, the present invention relates to a color-image readout lens used for reducing or enlarging an image and an image readout apparatus using the same.
2. Description of the Prior Art
Image readout lenses used in facsimile machines, image scanners, and the like of a type forming a reduced or enlarged image of an original are basically required to have a high resolution, large marginal light quantity, and minimized distortion at the imaging magnification used.
Known as an imaging lens which satisfies these requirements and reduces the weight and cost of the lens system and accordingly the weight and cost of the optical apparatus as a whole is, for example, that disclosed in commonly assigned Japanese Unexamined Patent Publication No. 7-104185, in which the number of lens elements is reduced to 4.
Though the above-mentioned four-element imaging lens disclosed in Japanese Unexamined Patent Publication No. 7-104185 favorably corrects both image surface curvature and distortion, its correction of chromatic aberration may be insufficient as a color-image readout lens.